It is known to use trim planes or hydroplanes, mounted from the transom to lower the bow of boats with planing hulls to reduce the time it takes to achieve the planing condition. However, the ability to control the wetted area of planing hulls has been narrowly limited to the single function of forcing the bow down by the use of transom-mounted trim planes. However, this single function is insufficient for various hull designs and sea conditions. Namely, there is a need for a hydrofoil system that will not only lower the bow, but raise the bow, improve lateral stability and assist in steering the boat as may be required for various hull designs and sea conditions.
An understanding of the contribution made by the present invention requires an understanding of planing boat hulls and previous hydrofoil designs or trim planes for planing hulls. Boats having planing hulls are designed to operate most efficiently at speeds where the hull "planes" on top of the surface of the water and a minimum area of the hull is in contact with the surface of the water. Typically, about one-half to two-thirds of the hull surface area is wetted at planing speeds. However, the extent of the wetted area may vary. With hulls having a transom deadrise, or an upward angle from the keel to the chine, of 10 degrees or more, less than one-half of the hull area may be wetted at planing speeds. Depending upon the hull design, as little as one-fourth of the hull area may be wetted during high speed operation.
When a boat accelerates, the natural tendency of the boat is to push the stern down and raise the bow. This stern-down, bow-up position is an inefficient use of engine power and fuel. Because the planing condition of the hull increases both speed and fuel efficiency, the primary goal of most hydrofoil or trim planes designs is to force the bow down to a horizontal angle thereby promoting planing of the hull and reducing the time for the boat to achieve the planing condition. Unfortunately, the existing designs perform this function only and do not address other performance and handling problems that arise.
For example, when the sea conditions are quite rough, it is desirable to raise the bow thereby causing the face of the waves to hit the boat hull rather than the tip of the bow causing the boat to take on water. Further, as stated above, many planing-type boat hulls employ a transom deadrise When the transom deadrise, or angle from the keel to the chines, is 10 degrees or more, the boat is less stable because the hull is not flat, but is V-shaped. Therefore, extra stability it desirable, especially during rough sea or water conditions Previous hydrofoil designs do not address this lateral stability problem.
Further, prior hydrofoil designs fail to acknowledge that dual hydrofoils can act as a quasi-rudder and assist in the steering and control of the boat. This additional function of the hydrofoils is desirable for rough handling boats and would be essential if the rudder system broke or because dysfunctional.
Thus, there is a need for transom-mounted hydrofoils that not only act to lower the bow, but also act to raise the bow and provide lateral stability and directional control. Hence, the opportunity to add additional safety and handling features to a boat with a planing-type hull should not be foregone as it is when current hydrofoil or trim systems are employed.